The present invention is related to a method for forging/molding a coarse blank of an aluminum transmission shaft. According to this method, burn-in softened aluminum material is first forged and molded into a blank body of the transmission shaft and then the blank body is continuously secondarily forged and molded into a coarse blank of the transmission shaft.
FIG. 5 shows an existent transmission shaft of a vehicle. The transmission shaft has a middle elongated shaft rod 81 and two pivot heads 92, 93 disposed at two ends of the shaft rod 81. The pivot heads serve as universal joints. In order to have a sufficient structural strength, the pivot heads have a size larger than the diameter of the middle shaft rod. Conventionally, the pivot heads and the shaft rod are separately manufactured and then the pivot heads are connected with two ends of the shaft rod by means of welding or fusion. According to such manufacturing procedure, the production efficiency is poor. Moreover, in order to have lightweight vehicle parts, the traditional transmission shaft is replaced with aluminum transmission shaft. For having sufficient strength of the middle shaft rod of the aluminum transmission shaft, the blank of the transmission shaft is first forged and then the blank is drilled into a hollow shaft rod. According to such measure, a great amount of aluminum material is wasted. Also, it is time-consuming to drill the blank of the transmission shaft. As a result, the manufacturing cost for the transmission shaft is high.